U.S. patent number 5,146,933 [Application Number 07/764,560] was granted by the patent office on 1992-09-15 for implantable prosthetic device and tethered inflation valve for volume.
This patent grant is currently assigned to Dow Corning Wright Corporation. Invention is credited to Lawrence M. Boyd.
United States Patent |
5,146,933 |
Boyd |
September 15, 1992 |
Implantable prosthetic device and tethered inflation valve for
volume
Abstract
According to the invention, there is provided an implantable
prosthetic device inflatable by a self-contained resealable valve
in combination with an external locator for determining the
position of the valve. The prosthesis includes a flexible outer
envelope defining a closed lumen and having a valve attached to an
area of the envelope with indicia on the valve responsive to the
external locator for determining the position of the valve. A
plurality of spaced sensors are each fixedly arrayed on the locator
so that when the sensors are in a certain non-juxtaposed
relationship with the indicia the sensors orientate with one
another, signifying a true location of the valve. A
multi-compartmental design having a tethered valve for selective
inflation of an inner lumen is also disclosed. The
tissue-contacting surface of the outer envelope is micro-textured
to minimize tissue capsule contracture.
Inventors: |
Boyd; Lawrence M. (Memphis,
TN) |
Assignee: |
Dow Corning Wright Corporation
(Arlington, TN)
|
Family
ID: |
25071068 |
Appl.
No.: |
07/764,560 |
Filed: |
September 20, 1991 |
Current U.S.
Class: |
128/899;
623/17.12; 623/23.67; 623/8; 623/901 |
Current CPC
Class: |
A61F
2/12 (20130101); A61B 90/02 (20160201); Y10S
623/901 (20130101) |
Current International
Class: |
A61B
19/00 (20060101); A61F 2/12 (20060101); A61B
019/00 () |
Field of
Search: |
;623/7,8,11,901
;128/899,898 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Ion-Beam Microtexturing of Biomaterials", Medical Device &
Diagnostic Industry, vol. 6, No. 4, Apr., 1984 623-8. .
Surgical Technique, "Tissue Expansion-Guidelines Case Analysis", by
Gordon H. Sasaki, M.D., 1985, Published by Dow Corning Wright
Corporation, Arlington, Tenn. . .
Pending U.S. patent application Ser. No. 402,745 filed Sep. 4,
1989, Inventor: James M. Curtis re: Method of Manufacturing an
Implantable Article Provided with a Micropillared Surface..
|
Primary Examiner: Frinks; Ronald
Attorney, Agent or Firm: Chiatalas; John L.
Claims
What is claimed is:
1. An implantable prosthetic device inflatable by a self-contained
resealable valve comprising:
a outer flexible elastomeric envelope;
an inner elastomeric envelope spaced inwardly from the outer
envelope, respectively defining an outer closed lumen and an inner
closed lumen nested within the outer lumen;
a resealable injection valve attached to a selected area of the
outer envelope, the inner envelope being tethered to the valve and
spaced inwardly from the selected area by a fill-tube for directly
inflating the inner lumen.
2. An implantable prosthetic device inflatable by a self-contained
resealable valve comprising:
a first flexible elastomeric envelope;
an second elastomeric envelope joined with the first envelope along
a common surface, respectively defining first and second closed
compartments;
a resealable injection valve attached to a selected area of the
first envelope, the second envelope being tethered to the valve
through the first compartment and spaced from the selected area by
a fill-tube for directly inflating the second compartment.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to prostheses which are inflatable after
implantation by means of resealable valves, and particularly to
configurations of such valves.
2. Description of the Prior Art
During plastic and reconstructive surgery, it is often necessary to
implant an inflatable prosthesis as a means of expanding the tissue
and skin in a localized area of the body. This can be done either
with a short term or "long-dwelling tissue expander device". Both
types of devices require that progressive injections of
volume-expanding fluid be made by the physician through a
self-sealing valve during successive postoperative outpatient
procedures. This is preferably done by percutaneous injection of a
silicone gel, saline or other fluid through the valve into a
reservoir to fill the lumen of the prosthesis; however, it is often
difficult to locate the injection valve among the surrounding
tissue. Various means have been employed to determine the location
of such valves, including manual palpation, as well as external
magnetic devices which sense the position of magnetic material
within the valve.
An example of a magnetic locator which is used to find the
injection reservoir in a mammary prosthesis is shown in U.S. Pat.
No. 4,467,125; however, the device is principally concerned with
providing a reinforcing member surrounding the juncture of the
valve and outer envelope, intended to prevent the envelope from
folding over upon itself during implantation. A similar product is
currently sold under the name "MAGNA-SITE", by McGhan Medical Corp.
of Santa Barbara, Calif. The magnetic locator device sold with this
product resembles a simple stud finder like those used in the
carpentry trade, e.g., that shown in U.S. Pat. No. 3,845,384.
U.S. Pat. No. 4,222,374 discloses an external locating device
having a magnetic sensor which determines the position of an
implanted metallic cardiac infusion pump by direct juxtaposition of
the sensor with the ferro-magnetic element. However, there is no
reference of such a device being used to locate an inflatable
prosthesis, particularly a mammary implant.
Another concern with inflatable prostheses is the formation of a
tissue capsule surrounding the implant, which has been known to
contract around and, in some patients, significantly compress the
implant, causing a great deal of discomfort. Thickness of the
tissue which forms the capsule has been found to be an important
factor in the incidence of problems related to capsule contracture,
which is a complication requiring the physician to either
surgically or manually rupture the capsule.
One approach that has been suggested to avoid this problem is the
use of an implant having an outer envelope which comprises a
microtextured surface. The aim of providing such a service is to
disrupt the capsular architecture and cause ingrowth of the tissue
into the microtextured surface, which results in a thinner tissue
capsule and lessens the risk of problems due to capsule
contracture.
One such device, shown in U.S. Pat. No. 4,955,909, provides a
textured surface on the implant from a tetrafluoroethylene (Teflon)
that is fabricated in a net-like, three-dimensional grid
structure.
Another approach is discussed in the article "Ion-Beam
Microtexturing of Biomaterials", Medical Device and Diagnostic
Industry, volume 6, number 4, Apr. 1984 which describes the use of
ion-beam milling of a soft tissue prosthesis to produce
microprojections on the surface of the outer envelope and the use
of such implants to reduce capsule contracture.
Still another approach is suggested in U.S. Pat. No. 4,955,907,
particularly the use of expanded polytetrafluoroethylene filaments
which are attached to a stretch fabric backing in a loose weave
configuration. Alternatively, silicone molded in geometric patterns
may be employed to present the textured surface.
Another approach is discussed in U.S. Pat. No. 4,960,425, wherein a
surgical prosthesis having a textured exterior surface formed of
non-absorbent material free of pores and interstices is shown. The
implant disclosed in this patent is made by molding a silicone
envelope over a textured or porous mandrel with either hot or cold
compression platens, which are said to create minute indentations,
deformations and/or raised portions on the surface of the envelope
having a width from 0.0003 to 0.10 inches and a depth from 0.0003
to 0.030 inches, such that the general appearance of the prosthesis
is that of an opaque surface, slightly roughened at the touch.
Another approach, and one which is particularly preferred, is taken
by U.S. Pat. No. 4,965,430, assigned to the instant assignee. This
method prepares a three-dimensional mandrel by laser-drilling an
array of blind holes in the surface of the mandrel, used for
preparing a mould for a silicone envelope having an arrray of
micropillars corresponding to the pattern of blind holes.
Still another device having a micro-textured surface is shown in
U.S. Pat. No. 5,002,572, which discloses a mass transfer device
having a fluid diffusing or transmitting surface in contact with
the soft tissue, the tissue contacting surface being textured to
provide a regular pattern of micropillars at least 100 microns in
height with dimensions and interpillar spacing each no greater than
5000 microns.
A different approach to the above methods of avoiding capsule
contracture is shown in U.S. Pat. No. 4,531,244, specifically, a
mammary prosthesis having a plurality of firm protuberances
covering the outer surface of the envelope is said to result in
flow spaces so that, when the scar capsule contracts and compresses
the protuberances, the mammary prosthesis has a spacer for
displacement and remains soft. The patent further states that the
protuberances, which have a specified height of between 1000-10,000
microns and a diameter between 1000-10,000 microns. This
macrotextured surface is further said to provide greater localized
pressure in pounds per square inch against the scar capsule in
order to maintain a space for implant displacement.
In addition to the attention given above to valve location and
tissue capsule contracture concerns, there have been numerous
attempts to provide volume-adjustable, anatomically-shaped mammary
implants, including tissue-expander devices. Accordingly, various
valve and fill-tube designs have been proposed.
One approach has been to situate an injection valve and reservoir
at a location remote from the prosthetic implant, the valve being
coupled with a fill-tube feeding into a volume-adjustable lumen.
Such arrangements are shown in U.S. Pat. Nos. 4,773,908; 4,643,733;
and 4,944,749, and further embodied in various products sold by the
Mentor Corporation, Goleta, Calif., as the "Becker Expander/Mammary
Prosthesis". Once the prosthesis has been filled to the desired
level, the remote valve, along with the fill-tube which links the
valve to a fill port in the envelope, is uncoupled from the filling
port and, once surgically removed, is not intended to be
reconnected.
Another volume-adjustable prosthesis having self-contained
injection valves is shown in U.S. Pat. No. 4,433,440. A pair of
valves are joined with the outer envelope at a common area, unlike
than the remotely located Becker valve. One of the valves leads
directly into an inner lumen which is joined to the outer envelope,
while the other valve leads directly into the outer lumen which
surrounds the inner lumen. A difficulty in this type of device is
that differential protrusion/expansion of the prosthesis cannot
occur other than at the area where both of the valves are commonly
joined with the outer envelope, versus areas remote from the valve
site.
Accordingly there is still a need for a volume-adjustable
prosthesis, particularly a mammary implant which is capable of
assuming a variety of anatomical shapes. Further, there is a need
for providing an integral valve to allow such a volume-adjustable
implant to be filled to a desired level by a physician without
post-operative surgical intervention, particularly by means of an
external valve-location means that accurately determines the
position of the valve. Still further, there is a need to provide a
volume-adjustable prosthesis, particularly a mammary implant, which
resists problems due to capsule contracture.
SUMMARY OF THE INVENTION
According to the invention, there is provided an implantable
prosthetic device inflatable by a self-contained resealable valve.
The prosthesis comprises a first flexible elastomeric envelope and
a second elastomeric envelope joined with the first envelope along
a common surface, respectively defining first and second closed
compartments. A resealable injection valve is attached to a
selected area of the first envelope, the second envelope being
tethered to the valve through the first compartment and spaced from
the selected area by a fill-tube for directly inflating the second
compartment.
The accompanying Drawings, which are incorporated in and constitute
a part of this Specification, illustrate the preferred embodiments
of the invention and, together with the Description, serve to
explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view, partially cut away, of a prosthesis
with an inflation valve and a remote magnetic locator, according to
one embodiment of the invention, and wherein the injection valve is
tethered by a fill-tube to a volume-adjustable lumen of the
prosthesis;
FIG. 2 is a perspective view of the remote locator, according to
the invention;
FIG. 3 is a top view of the prosthesis and locator combination
according to the invention, showing the sensors of the locator
orientated with one another to signify a true position of the
valve;
FIG. 4 is a sectional view, taken along the lines 4--4 of FIG.
3;
FIG. 5 is a sectional view of the self-sealing injection valve and
reservoir, showing the self-sealing valve preferably containing a
magnet and being punctured by an injection needle;
FIG. 6 shows the connection of the tethered fill-tube leading into
the inner lumen from the valve reservoir, according to one
embodiment of the invention;
FIG. 7A shows a tissue expander having a rounded shape with a valve
of the type used in combination with the locator of the present
invention; and
FIG. 7B shows an asymmetric or differential tissue expander having
a self-contained valve, according to one preferred embodiment the
present invention;
FIG. 8 is an enlarged sectional view of an alternative injectable
valve assembly of the present invention; and
FIG. 9 shows a stacked tissue expander having a pair of valves each
with magnetic indicia, one of the valves being tethered for
adjusting the volume of a first lumen and the other valve leading
into a stacked lumen, according to another embodiment of the
invention.
DETAILED DESCRIPTION
References will now be made in detail to several embodiments of the
invention, examples of which are illustrated in the accompanying
Drawings.
A preferred embodiment of the inflatable prosthesis and valve
locator combination is shown in FIGS. 1-3. The combination
comprises a prosthesis, generally shown at 10, and a locator,
generally shown at 12. The implantable prosthetic device 10
comprises an inflation valve, generally indicated at 14 (See also
FIGS. 4-5, 7A, 7B, 8 and 9) which is designed to operate with the
external locator 12, allowing a surgeon to determine the position
of the valve for successive post-operative injections to fill the
prosthesis 10 to a desired volume. The prosthesis 10 comprises an
outer flexible envelope 16 defining a closed outer lumen 18. The
valve is provided with indicia in the form of
magnetically-responsive elements, such as the magnets 20 shown in
FIGS. 4, 5 and 7B, although other metallic elements could be used
provided they are magnetically-responsive. The magnets 20 are
preferably coated with a vapor-deposited polymer barrier, of the
type generally known in the art, to guard against metal ion release
from the magnet. Although it is preferred that magnetics be used,
it is understood that a person skilled in the art will appreciate
that other means could be used to signify the position of the
valve, which are capable of being determined by external locator
devices of the type generally described in this Specification. The
valve has a generally circular cross section and is preferably
joined to an area of the outer envelope which can vary in diameter,
shown by the concentric phantom lines 22, as will be appreciated
below.
The locator 12 comprises a base 24, including a plurality of
sensors 26, 28, each of which preferably comprise a magnetic
compass needle 30. The needle 30 is allowed to freely orientate
with either the north or south magnetic pole within a closed recess
in the base 24. The needle may either be rotatably mounted on the
end of a pin 32 or may be free-floating in a fluid that is sealed
within the recess (not shown). It will be further understood by
those skilled in the art that metallic elements could be provided
in the sensor 26 or 28 which would be responsive to a magnetic
element 20 in the valve assembly 14. It is important however, that
the plurality, in this case the pair of sensors 26 28 be spaced
from one another such that when the locator 12 is manuevered into
position over the valve 14 the pair of north or south indicating
needles 30 orientate with one another and define a third point,
shown by the target opening 34 which indicates a true position of
the valve 14. In this regard, the magnetic indicating system is
somewhat similar to the "triangulating" approach used in
navigation, however, this principle has been adapted specifically
for use in a device for precisely locating the injection valve of a
prosthesis, such as the preferred embodiment of a mammary
prosthesis shown in FIGS. 1, 4, 7A-7B and 9. It is preferred that
both needles have the same magnetic pole orientation, for example,
either both north or both south indicating magnetic elements, so
that the heads of both point in the same direction, i.e., the
target circle 34. Of course, the needles actually move
independently of one another and it is the intersection of their
respective axes that defines the target when accurately aligned. It
would be further appreciated by those skilled in the art that three
or more needles could alternatively be used in a triangular base
with a center target (not shown) located at the centroid of the
triangle defined by vertices corresponding to each magnetic needle.
FIG. 2 shows the needle 30 in a non-orientated position, while FIG.
3 shows the needles pointing toward the target 34 to signify the
true location of the underlying valve 14.
Thus, a physician (or nurse) is able to precisely locate the
injection valve in successive office visits of the patient, without
further surgical intervention needed other than to remove a tissue
expander in exchange for a long-dwelling implant.
An advantage of the invention is that the locator actually guides
the user (physician or nurse) to the valve site by signifying the
proximity and direction of approach of the valve by the user. This
is in distinct contrast to the pivoting-types of stud-finders
shown, for example, in the above U.S. Pat. No. 3,845,384, which do
not guide the user toward the valve location but rather require
multiple passes over the site to ascertain the proper
coordinates.
As shown in FIGS. 1, 4 and 7A-7B, the prosthesis 10 may assume a
variety of three-dimensional shapes, which are adapted to the
specific needs of the patient. For example, FIG. 1 shows a
pendulous or ptotic shape, as do FIGS. 4 and 7B, while FIG. 7A
shows a rounder shape.
In another embodiment of the invention, it is an object to provide
an implant which, when inflated, will assume an asymmetrical shape
as described immediately above, thus meeting the needs of
particular patients. It has been known to provide an implantable
tissue expander (either long-dwelling or short-term) or other
prosthesis of a dual-lumen construction. However, such
constructions have conventionally been designed so that the inner
and outer envelopes of the respective lumens are joined together at
an area where the valve is located. Thus, differential tissue
expansion is restricted to the area of the outer envelope
immediately surrounding the valve. In contrast, it is an object of
the present invention to provide tissue expansion at an area remote
from the valve in achieving a preferably asymmetrical or pendulous
shape, as will be described below.
Another preferred embodiment of a mammary implant 10 is shown in
FIGS. 1, 3, 4 and 9. Particularly, in FIGS. 1, 3 and 4, the
prosthesis 10 further comprises a nested multi-compartmental
arrangement, unlike the embodiments shown in FIGS. 7A-B, which
comprise a single lumen, and FIG. 9, which is a stacked
multi-compartmental design. Rather than the single lumen 18' shown
in FIGS. 7A-7B, the dual lumen embodiment as shown in FIGS. 1, 3, 4
and 9, comprises an outer lumen 18 which is defined by the outer
envelope 16 and an inner closed lumen 36 which is defined by the
inner envelope 38, shown partially broken-away in FIG. 1. The
injection valve 14 and inner lumen 36 are tethered by a fill-tube
40, shown also in FIGS. 3-6 and 9, whereby fluid injected into the
valve 14 flows through the fill-tube directly into and inflates the
inner lumen 36, without inflating the outer lumen 18. Therefore,
the prosthesis 10 shown in FIGS. 1, 3 and 4, is inflatable
post-operatively only in the region occupied by the inner lumen
36.
During, manufacture, the outer lumen 18 is permanently filled with
silicone gel to a desired level through a conventional silicone
elastomer patch which is then sealed. It is preferable to fix the
position of the inner lumen 36 by adhering the inner envelope 38 to
the outer envelope 16 in a desired area, as shown by FIGS. 1 and 4,
using a conventional medical grade silicone elastomer
composition.
The prosthesis 10 in one of its embodiments has a ptotic shape
(FIGS. 1, 3-4, 7B and 9) with a rounded anterior surface 42 (FIG.
3), which is intended to protrude anteriorly following
implantation, and a flattened posterior surface 44 (FIG. 1), lying
flat against the tissue. Moreover, it is desirable to fill the
inner lumen with saline postoperatively from the upper or rounded
surface 42 of the prosthesis which is accessible to injection by
the surgeon. It will be understood that gel/saline, gel/gel,
saline/saline or other combinations of biocompatible fluids could
be used to fill the various lumens of the implant, depending on the
desires of the physician. As the inner lumen 36 of the implant 10
is filled with saline (preferably) upon progressive injections of
fluid through the valve 14, the volume of the inner lumen 36 is
increased as represented by the various positions of the inner
envelope 38, shown in phantom in FIG. 3. Such a volume increase
results in an increased projection of the inferior portion 43 while
maintaining minimal projection of the superior portion 45 of the
anterior surface 42.
With respect to implantation of a percutaneous tissue expander, a
preferred surgical technique is set forth in "Tissue
Expansion-Guidelines Case Analysis", by Gordon H. Sasaki, M.D.,
dated 1985 and published by Dow Corning Wright Corp., Arlington,
Tenn., the entire disclosure of which is hereby incorporated by
reference and relied-upon. It is important that certain details be
observed for the sake of safety and efficacy in implanting the
device described herein. Namely, the surgeon should select an
incision size and location which allows for creation of a
well-defined, dry pocket; allow for insertion of the implant
without distortion; and allow for ready digital access to the
pocket to ensure flat implant placement and smoothing of the
implant surface. The pocket size created by the surgeon should be
of sufficient size to allow the implant to lie flat in the pocket.
The measures will reduce the wrinkling of the implant surface. As
mentioned above, the inflation valve must be placed to ensure that
the injection port is readily locatable, and secure in its pocket.
With respect to wrinkling, it is important that, when the tissue
expander is inserted, the expander envelope is initially flaccid,
i.e., redundant and folded. Injection of saline into the tissue
expander to the limits of tissue tolerance is recommended following
insertion to minimize the wrinkling and folding of the expander
envelope. Once the tissue expander is in its pocket, it should be
smoothed out to minimize fold formation. An advantage of the
externally-locatable inflation valve of the invention is that, if
the projecting fold produces ischemia or thinning of overlying
tissue during the expansion process, the tissue expander can be
partially deflated for two to three weeks without surgical
intervention, allowing tissue stabilization. Periodic expansion may
then be resumed. If a projecting fold remains a problem, the
implant should be deflated and an attempt made to manipulate the
fold to another area. If these attempts are still unsuccessful and
buckling of the expander envelope remains a problem, the implant
should be removed.
Folds in the tissue expander may also result in weakening and/or
deflation of the unit through abrasive micro-motion of the envelope
against itself. Tissue expanders left under-inflated for a long
period of time or folded envelopes under pressure have developed
leaks at the folds resulting in deflation of the unit. Care must
also be taken to avoid inadvertent post-operative perforation of
the tissue expander during inflation. The location and orientation
of the inflation valve should always be confirmed prior to
inflation. The inflation needle should always be inserted in the
center of the injection port generally perpendicular to the face of
the valve (see FIG. 5). Overly acute angles of insertion should be
avoided. Moreover, care should be taken so that the envelope does
not overlap the valve as this could result in perforation of the
envelope during inflation.
The self-contained valve of the present invention, versus the
remote valve arrangements used in the prior art tissue expanders,
for example the "Becker" products, has the advantage of requiring
no distant site for valve placement, thus minimizing the time and
trauma for placement and removal of the tissue expander. Also the
inherent design of the self-contained valve reduces tube kinking or
disconnection. However, as mentioned above, care must be taken to
avoid inadvertent puncture of the envelope of the expander. With
regard to implantation at the time of surgery the base dimensions
of the selected expander may be outlined on the patient using as a
guide an appropriate template. A pocket 1 cm larger than the
expander will allow the expander to lie flat and helps to prevent
buckling of the implant which could lead to an extrusion during
expansion.
Particularly in older patients, an anatomicaly-shaped, pendulous
expander device should typically be selected for expansion. The
tear-drop shape with the integral valve, allows for a broad base
and greater projection at the lower half of the expander which, in
turn, allows for significant portion of expansion to occur at and
below the infra mammary line. Thus, it will be apparent to those
skilled in the art that there has been described herein a preferred
method of using the subject tissue-expander device.
The particular structure of the integral inflation valve 14 will
now be discussed. Referring to FIGS. 4, 5, 7B and 8, the valve 14
comprises a soft ring 46, a self-sealing sheet of silicone material
48 joined to a silicone valve case 50 and a metal cup 52, defining
a reservoir 54. The magnet 20 is encased in the cup 52 and has a
needle stop 56 overlying the magnet. The soft ring 46 and
self-sealing material 48 are joined to the outer envelope 16 by a
silicone medical grade adhesive, by simultaneous curing, or other
suitable for joining the materials permanently together. FIG. 8
shows the attachment of valve 14 to envelope 16 by means of a layer
57 of medical grade elastomer. It should be noted that the valve
assembly 14 is on the internal surface of the outer envelope 16
and, thus, is situated within the outer lumen 18 such that the
valve 14 does not protrude above the outwardly surface of the outer
envelope 16. The fill-tube 40 penetrates the case 50 and the cup 52
and is in fluid communication with the reservoir 54. Fluid enters
the reservoir 54 through the injection needle 58, shown in FIG. 5,
and flows from the reservoir 54 through the fill-tube 40 in the
direction of arrow 60 toward the inner lumen, as can be appreciated
from FIG. 4.
Referring to FIG. 8, there is shown an alternative arrangement of
the soft ring 46 in terms of its attachment to the outer envelope
16. Specifically, ring 46 is of a one-piece construction with
downwardly projecting flanges 62 that are unsecured to the outer
envelope 16. The purpose of the ring 46, and particularly the
flanges 62 is to make the valve assembly less externally palpable
during use of the implant 10.
Referring to FIG. 6, the fill-tube 40 passes through a port,
generally indicated at 64 (also shown in FIGS. 1, 3, 4 and 9) which
leads into the inner lumen 36. The fill-tube 40 passes through a
sleeve 66 that is integral with a base 68 which forms a T-shape
connector. The base 68 is adhered to the internal surface of the
inner envelope 38 by means of a suitable medical grade silicone
elastomer material. Both the fill-tube 40 and sleeve 66 are
preferably made of a silicone tubing material.
Referring to FIG. 9, there is shown a prosthesis 10 having a
stacked design wherein a first envelope 70 is joined to a smaller
second envelope 72 in a selected area to provide localized or
areolar expansion. The first envelope defines a closed first
compartment 74 and the second envelope 72 defines a second closed
compartment 76. The second compartment 76 is situated on the
inferior portion 43 of the anteriorly-projecting surface 42 of the
first envelope 70 so as to impart an asymmetrical shape to the
prosthesis 10. The first compartment 74 is supplied by a
self-contained valve 78 which is tethered by a fill-tube 80 to the
first compartment 74. The fill tube 80 extends between a reservoir
in the valve 78 and an inlet port 82, such that fluid injected into
the valve 78 flows through the tube 80 directly into the first
compartment 74, expanding its volume. The volume of the relativley
smaller second compartment 76 may also be adjusted by means of the
self-contained valve 84 which is spaced from the valve 78, that is,
injection of fluid into the valve 84 flows directly into the second
compartment 76, thus the valve 84 is not tethered, as is the valve
78. It is possible to distinguish the spaced valves 78 and 84 from
one another by using magnets of differing orientations in each. For
example, the valve 78 may have a north pole-facing outward magnet,
while the valve 84 can have a south pole-facing outward magnet.
Accordingly, separate locators (not shown) may be used for each of
the valves, for example, the compass needles on one of the locators
can indicate the north pole, while the compass needles in another
locator can indicate a south-pole. Alternatively the same locator
can be used with dual-arrow needles (not shown) which point with
arrows of one color to one valve and with arrows of another color
to the other valve. This allows for a multi-compartmental stacked
adjustable implant to be used without remote valves. An advantage
of this particular arrangement is that a large second compartment
74 may be used, since the first compartment need not be punctured
for inflation.
An advantage of the long-dwelling tissue expander device according
to this invention is that the breast size may be changed as the
patient gains or loses weight, further a pendulous shape may be
obtained which more closely resembles a natural breast,
particularly in larger and/or older patients. In contrasts, the
long-dwelling tissue expanders of the prior art, for example, the
"Becker Tissue Expander" cannot be inflated once the fill-tube is
pulled out of the lumen with the remote valve.
Another feature which can be used with any or all of the
embodiments of the invention shown herein, is an outer envelope 16
having a micro-textured surface, as shown in FIG. 5. The
micro-textured surface is formed by dipping a textured mandrel into
a bath of silicone fluid and curing the silicone fluid under
pressure then stripping the finished envelope from the mandrel. A
preferred method of fabricating the mandrel is disclosed in U.S.
Pat. No. 4,965,430 to Curtis, assigned to the assignee of the
present invention, the entire disclosure which is hereby
incorporated by reference and relied upon. Likewise a preferred
method of preparing an envelope having a micro-textured surface in
accordance with the present invention, using the mandrel fabricated
in accordance with the above U.S. Pat. No. 4,965,430 is disclosed
in pending U.S. Pat. application Ser. No. 402,746, filed Sep. 4,
1989 in the name of James M. Curtis, assigned to the assignee of
the present invention, the entire disclosure of which is hereby
incorporated by reference and relied upon. The tissue-contacting
surface of the outer envelope 16 is micro-textured with a pattern
of micropillars 82, as shown in FIG. 5, which disrupt the
architecture of the fibrous tissue capsule formed around the
implant. As a result, the tissue capsule is much thinner and the
incidence of clinical capsule contracture problems is significantly
reduced. The micropillars 82 have a generally frusto-conical shape
such that the diameter of the appex is less than the diameter of
the base where the micropillar joins the substrate of the envelope
16. The preferred structure of the micropillars 82 is discussed in
detail in the above U.S. Ser. No. 402,746. Several advantages
result from the structure of the micropillars 82, including the
ease in stripping of a tissue expander from the body prior to
insertion of a long-dwelling implant. Further, the frusto-conical
shape is believed to reduce irritation of the tissue capsule which
can result in microbleeding, as is the case with certain prior art
textured implants, discussed above, which have conical, pointed
projections. As a result, the surgeon has significantly less
difficulty with the tissue capsule after removing the expander to
prepare for implanting the long-dwelling prosthesis.
While the invention has been described with respect to certain
embodiments, it will be obvious that various modifications may be
contemplated by those skilled in the art without departing from the
scope of the invention as hereafter defined by the following
claims.
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